Routers are used to remove material from a workpiece for decorative or functional purposes. In particular, routers may be useful in performing cabinetwork, cutting grooves in the surface or edges of a material, and applying a decorative border to a material through fluting or beading. In general, there are two types of routers, namely fixed base routers and plunge base routers. Both types of routers include an electric motor having a rotating shaft mounted vertically within a housing. The motor shaft terminates with a chuck, clamp, or collet for interchangeably securing a cutting tool, referred to as a router bit, to the shaft for rotation with the shaft. Fixed base routers and plunge base routers exhibit structural differences that affect the method by which the routers are operated.
Fixed base routers include a motor unit coupled to a base having a motor mount, two opposing handles, and a work engaging surface. The motor mount is connected to the top of the work engaging surface. The handles are connected to the motor mount and/or the top surface of the work engaging surface. A router bit, coupled to the motor unit, is configured to extend through an opening in the work engaging surface. The amount the router bit extends from the work engaging surface is adjustable depending on the position of the motor unit relative to the motor mount. In particular, the motor mount may include a plurality of different positions in which the motor unit may be locked. The plurality of positions enables a user to make grooves or cuts of a particular depth, depending on which position is selected. In general, a user operates a fixed base router by precisely guiding the rotating router bit around the edges or surface of a workpiece, thereby causing the bit to cut and remove portions of the workpiece at a fixed and predetermined depth.
Plunge base routers include a carriage, two opposing handles, a base plate, and two plunge posts. The plunge posts extend perpendicularly from the base plate and extend into channels formed in the carriage. The carriage is configured to house an electric motor, wherein the rotating shaft of the electric motor extends downward from the carriage toward the base plate. The opposing handles are connected to opposite sides of the carriage. Biasing members are configured to bias the carriage in an upward direction away from the base plate so that the motor shaft and the router bit, if one is attached, are positioned above the base plate, out of contact with a workpiece. A user may apply downward pressure upon the opposing handles, to slide the carriage down the plunge posts toward the workpiece until the router bit extends below the base plate by a predetermined distance. Thus, the term “plunge” refers to the ability of a plunge base router to direct a router bit into contact with a workpiece from the upper position in which the router maintains the rotating router bit above the workpiece, to the lower position in which the router bit is forced into contact with the workpiece. Note that the router may be secured in the lower position with a locking member, thereby permitting a user to relax the downward pressure upon the opposing handles during the routing process. Upon releasing the locking member and the downward pressure on the handles, the biasing system forces the carriage to slide up the plunge posts to the upper position, thereby removing the router bit from contact with the workpiece.
Before plunging a router bit in to a workpiece, a user must first determine the desired depth of cut, referred to as the plunge depth. Known routers include adjustment capabilities that permit both a course depth adjustment and a fine depth adjustment. In particular, course depth adjustments are made by securing an adjustable rod to the carriage a predetermined distance above a stop tab. The carriage may then be depressed upon the plunge posts until the adjustable rod contacts the stop tab. Likewise, fine adjustment mechanisms permit a user to adjust the vertical position of the router bit and carriage after the lock mechanism has secured the router in the lower position. Often fine adjustment mechanisms include an adjustment knob located at the top of one of the plunge posts. Rotation of the knob causes an adjustment member to move the carriage up or down precisely.
Known fine adjustment mechanisms work well; however, the configuration of known mechanisms often results in an overall increase in the height of the router, thereby limiting the environments in which the router may be utilized. Thus, a router having a fine adjustment mechanism that does not increase the overall height of the router is desirable.